Only 47 of 100 senators attended the 2:30 briefing, leaving dozens of chairs in the secure meeting room empty as Clapper, Alexander and other senior officials told lawmakers about classified programs to monitor millions of telephone calls and broad swaths of Internet activity. The room on the lower level of the Capitol Visitor Center is large enough to fit the entire Senate membership, according to a Senate aide.

The Hill was not provided the names of who did, and who didn’t, attend the briefing.